Machine designers when faced with the problem of motion transmission have come up with various ingenious solutions to the problem, particularly, where intermittent motion must be transmitted or where special requirements are laid upon the machine, as for instance, unidirectional motion transmission, or in the case of rotating machines, limitation to a single sense of rotation. Where gearing is employed, recourse may be had to specific tooth forms in order to obtain specific limitations. Thus, should one attempt to turn the ring gear 1 in Swiss Pat. No. 321,237 in a clockwise sense, butting will occur between the internal teeth thereon and the teeth on the satellite pinion 6 whereby the two are locked together. Rotation in the counter clockwise sense of ring gear 1 however is freely permitted this owing, of course, to the specific tooth form chosen.
Should rotational transmission be desired in either sense of rotation, recourse may be had to the well-known Maltese cross mechanism, otherwise known as the Geneva wheel. Many variants of this particular mechanism are known. Among others may be cited the several variations shown in Swiss Pat. No. 599, 485. In this case, the driven member as well as the driver may have asymmetric toothing arranged in two planes. Here the motion transmitted is converted from steady motion into step by step motion, and owing to the particular construction of the toothing and the arrangement in two planes thereof, locking occurs between each step. A specific utilization for such mechanism has been shown in conjunction with a calendar mechanism as employed in a timepiece such as a watch.
As already mentioned, the foregoing mechanism provides a conversion from a continuous rotational motion to a stepping motion. It will thus be unsuitable for application in the context of the present invention wherein the driving source may already be provided with a stepping motor. Thus, for instance, in the case of a quartz controlled timepiece utilizing a miniaturized stepping motor and a time display employing time indicating hands, it is desired that forces occurring in the mechanism through sudden changes of directional motion, as may be expected during normal wearing of the timepiece, will not be transmitted from the time display back through the various gearing to react on the stepping motor. Since, however, the stepping motor itself already provides a step by step motion, it is desired to eliminate such further step by step motion as might be impressed on the existing movement. Thus, the gear train, such as illustrated in Swiss Pat. No. 599,485 would not be suitable. Although the present invention provides asymmetric teeth occurring in two planes the basic difference is that in both driving and driven member the teeth in each plane are a reflection about a diametral line of the teeth occurring in the other plane. Owing to the differences in asymmetrics, locking, however, may be expected as in the case of the Swiss Pat. No. 599,485 should one attempt to transmit rotational motion from the normal driven member to the normal driving member.